Add :uri and :scheme/:host keys to exceptions raised by
`validate-uri` for better error diagnostics. Also fix a bug
where (str url) was used instead of (str uri) in the
host-missing exception path.
Update the existing blocked-target test to verify the new :uri
key, and add three new tests covering scheme rejection, missing
host, and DNS failure error paths. All 27 tests pass with 60
assertions and 0 failures.
Signed-off-by: Andrey Antukh <niwi@niwi.nz>
1b6b367951